Age: 495
Gender: Female (Purebred Demon (Devil))
Hair color: Light Pink
Eye color: Golden

Echidna is the demon queen leading the latest invasion on mankind in search of the Philosopher's Stone. After being defeated by Leo Demonheart, she was driven into retreat, but seeks to rebuild her army.

She is a woman of average height, has horns, knee-length pink hair, and deep, golden-colored eyes. She wears one pair of red earrings, thigh-high boots, a red dress, and a black belt adorned with a golden suspender. Even though she has a young and beautiful woman's appearance, she is over a hundreds years old.

It is said that she is an unruly and cruel person. Despite these rumors, Echidna is generally easy-going, cheerful, and relaxed. As long as she isn't directly provoked, she's perfectly fine with "live and let live," although she occasionally voices the desire to burn up people en-masse when she gets impatient. At her core, Echidna is a very kind and noble woman. The reason she pursues the Philosopher Stone is because she wants to help the Demon World and give her fellow demons a peaceful place to live free of fights and bloodshed. Unlike her predecessors, she dislikes unnecessary violence. This is shown during the invasion of the human world: to keep casualties to a minimum, she gave the order to avoid killing whenever possible and rule the occupied territories peacefully.

Echidna deeply cares for her subjects and does her best to treat them with respect and kindness, taking time to thank even the lowest level subordinates for their efforts. She even organized a private dinner for Lord Onyx because wanted to personally meet and thank him for his work despite being a newbie in their army. Despite maintaining the affect of a commander in public, she has a soft spot for her generals, worrying about their problems and safety. This is especially true for her second-in-command Shutina, having known her the longest.

Although she is prepared to destroy mankind in order to retrieve the Philosopher's Stone, Echidna has nothing against them. She doesn't blame them for considering her army villains. She does not discriminate among humans and treats them all with respect, and she'll welcome any who wish to join her army. The one exception to her kindness is Leo Demonheart, the lone destroyer of her army: it is for that reason she refuses to accept him when he applies to join her ranks. She gets incensed at the mention of his name, and blasts him with fire magic whenever she sees him. Despite this, she doesn't actually hate Leo, but understands that he was simply defending humanity when he fought her.

Though an imposing and intelligent woman, she has a bit of a childish and comedic side. This side shows when she's drinking alcohol, but she can quickly get serious again if the situation calls for it.

(Source: Yuusha, Yamemasu Wiki)